This proposal describes a simple, portable, and cost-effective technique that detects lung cancer from human breath rapidly and non-invasively. This device is akin to an electronic nose that smells the characteristic odor of cancer from a person's breath. Lung cancer is the most common cancer worldwide and causes more deaths than any other cancer. Early detection of lung cancer drastically improves the rate of survival of patients (from 15 to 50 % over 5 years). Current methods for diagnosing lung cancer can be cumbersome, invasive, and often detect the disease after a substantial decline in health has occurred. New, robust, and simple methods for detecting lung cancer are necessary for reducing the mortality from this disease. A promising, non-invasive approach for detecting lung cancer relies on examining the chemical composition of exhaled air. Researchers demonstrated that dogs can be trained to recognize lung cancer with 99% accuracy by smelling exhaled air obtained from patients at all stages of the disease. Researchers have also identified specific patterns of chemicals present in exhaled air of lung cancer patients that are distinct from those of healthy humans. A technique capable of correlating the chemical composition of exhaled air with early-stage lung cancer has the potential to improve the rate of survival of patients with thi disease. The goal of this research is to make an array of five sensors for identifying the pattern of five distinct chemicals in human breath. The presence of four of these chemicals will indicate lung cancer and the remaining one will help differentiate lung cancer from other types of respiratory disorders. Each component of an array comprises a bundle of carbon nanotubes-functionalized with receptors designed to capture a specific volatile analyte-positioned between two electrodes. The binding of the analyte to the receptor on the surface of the nanotube alters the conductance across the array of nanotubes; this change in conductance correlates with the amount of volatile analyte in human breath. Ultimately, we hope that this method will be simple, sensitive, and inexpensive enough for early diagnosis of lung cancer, and for routine monitoring of the progress of disease in patients already diagnosed with lung cancer.